Steam engine with self-contained valvular mechanism



Jan. 2, 1968 HARVEY ETAL 3,361,036

STEAM ENGINE WITH SELF-CONTAINEQ VALVULAR MECHANISM Original Filed Feb. 10, 1964 Fla. 1

Meier/n5 valve INVENTORS ROBERT HARVEY FIG, 2 F. LEO NLOMAGLIO BY W? T x- ATTORNEY United States Patent 3,361,036 STEAM ENGINE WITH SELF-CONTAINED VALVULAR MECHANISM Robert Harvey, Sudbury, and Francis Leo Lo Maglio,

Dracut, Mass, assignors to Thermo Electron Engineering Corp., a corporation of Massachusetts Original application Feb. 10, 1964 Ser. No. 343,317, now Patent No. 3,279,326. Divided and this application May 5, 1966, Ser. No. 568,tl76

3 Claims. (Cl. 91-224) ABSTRACT OF THE DISCLGSURE A reciprocating engine with self-contained valvular mechanism including a piston actuated admission valve with the piston carrying spring actuated exhaust valves responding to variations in pressure within the cylinder to allow the working fluid to exhaust at a predetermined pressure.

This application is a division of application Ser. No. 343,817, filed Feb. 10, 1964.

This invention relates generally to steam engines and more particularly to a miniaturized steam engine adapted for use with a package or compact steam generator.

With the advent of military forces operating in remote regions of the world, a need has developed for a light weight, portable electrical generating unit that can be transported and operated by a field unit without the usual difliculties encountered in conventional electrical generating power unit. The usual difficulties which are inherent with conventional power plants are problems encountered with starting, ignition servicing, ingestion of water or other foreign matter into the exhaust or intake, hence int-o the engine.

Therefore, it is an object of this invention to provide a simple, novel and portable reciprocating steam engine which, adapted for use with a miniaturized steam generator, can be used for portable power generation.

Another object of this invention is to provide a direct expansion, closed system unifiow type reciprocating steam engine without piston rings or conventional valve timing mechanisms.

Another object of this invention is to provide a reciprocating engine having a tuned admission valve.

A further object of this invention is to provide a reciprocating engine in which the possibilities of contamination of the boiler water is minimal, since the cycle is a closed cycle, which is hermetically sealed.

A further object of this invention is to provide a relatively silent prime mover adapted for use with an electrical generator.

Another object of this invention is to provide a reciprocating engine Where the exhaust valve remains open during the return stroke thus maintaining the chamber at exhaust pressure and thus eliminating the back pressure on the piston during the return stroke.

Other objects of this invention will in part be obvious and will, in part, appear hereinafter.

Broadly stated, one feature of this invention is to provide a prime mover for use with a steam generator and in turn is utilized to drive an electrical generating unit which essentially must be portable and capable of relatively silent operation. Since the prime mover or engine can be operated in areas remote from repair and supply depots by average civilian and military perronnel, a further requirement is simplicity in operation and a design that eliminates constant adjustment of valve timing and the like. Consequently, the invention consists of a miniaturized reciprocating steam engine in which the admission valve is actuated by the piston travel and the open-time 3,36lfl35 Patented Jan. 2, i965 ice is determined by the natural resonant frequency of the admission valve mechanism. The engine therefore operates in direct relationship thereto eliminating valve gearing or eccentrics. The exhaust valves are located on the face of the piston, and utilize the cut-off principle to obtain the maximum exhaust emciency of the working fluid. Also taking into consideration the problems of initial cylinder condensation when the uni-flow principle is used, the exhaust valves and ports :are thus distinct and further removed from the admission ports so that the termination gradient existing between the cylinder walls and the admitting steam is kept at a minimum.

To the accomplishment of this and the foregoing related ends, the present invention then consists of the means hereinafter fully described and partially pointed out in the claims, the annexed drawings and the following description setting forth in detail certain means in the carrying out of the invention, such disclosed means illustrating however but one of the various Ways in which the principle of the invention maybe employed.

In the drawings:

FIG. 1 is a view in section of the with the piston at top dead center; and

FIG. 2 is a side view in section of the reciprocating engine with the piston on the downward stroke or at bottom dead center.

Reference is now to be had to the drawings wherein an illustrative embodiment of the reciprocating engine, a construction made in accordance with the present invention and designated by the numeral Ill. The engine 10 consists primarily of a cylinder 12 with cylinder Walls 14 formed of graphite of a pure high density or other materials having similar properties, and a piston 16 having a skirt 18 adapted for reciprocating movement within the cylinder 12. At one end 20 of the cylinder the exhaust manifold 22 is secured by any suitable means having piping 24 adapted to convey exhaust fluid to a condenser (not shown) or the atmosphere. The piston rod 25 extends from the piston 16 through the exhaust manifold 22 and through suitable seals 28 to a crank (not shown) where the reciprocating motion is converted to a rotating force through a cross-head, connecting rod and crankshaft (not shown) in the usual manner. concentrically disposed within the cylinder and extending upward from the lower head 30 is a guide 32 which surrounds a portion of the length of the piston rod 26 to serve as a retainer for a spring member 34; the spring member 34 is concentrically disposed around the piston rod 26 and normally bias the piston in the direction of the top cylinder head 36.

As shown in FIG. 2, the piston 16 has a recess 38 formed in the upper lateral surface thereof for a purpose to be set forth more fully hereinafter. Radially spaced from said recess and diametrically opposed to each other are exhaust ports 40 having integral valve seats 42 positioned within said valve seats 42 and adapted to seat therewith are exhaust valves 44 having resilient, non-metallic blocks or springs 46 bonded or secured in the upper surfaces for a purpose to be set forth more fully hereinafter. The valves 4-4 have stems 48 extending through the exhaust ports with spring members 50 concentrically disposed there around and adapted to bias the valves 44 away from the valve seats 42 so that in a non-operating condition or while the engine is at rest the exhaust valves 44 are normally open. The springs 50 are retained in assembly with the stems 48 by lock rings 51 snapped into engagement with the stems 48.

Extending upward from the guide, 32, are positive valve operating stops, 52, adapted to engage the bottom, 54, of the stems, 48, at or near the extreme end of the piston travel to ensure exhaust valve operation. Ports, 56, are cut through the guide, 32, to provide means for the egress of the exhaust steam into the cylinder proper.

reciprocating engine Positioned above the top cylinder head, 36, is a steam admission chamber, 58, having an admission valve, 60, spring biased into engagement with a valve seat, 62, formed in the cylinder head, 36, by means of a spring, 64. The admission valve, 60, has a stem, 66, maintained in alignment with the valve seat, 62, by non-metallic blocks disposed within a guide, 68. The lower surface of the valve, 6 3, has a flat surface adapted for engagement with the spring disposed in the recess, 38, formed in the head of the piston, 16.

Suitable piping, '70, conveys admission steam from the steam generator to the steam chamber, 58, and has a suitable by-pass line, '72, extending to initial metering valve, 74. The by-pass line, 72, is initiated by means of a push-button, 76, to open suitable valves located within the starting chamber to permit the flow of a metered amount of steam to the cylinder through a port, 77, when the admission valve, 60, is closed and is used primarily at the initial starting periods.

The top cylinder head, 36, and admission chamber, 58, are secured to the cylinder by headbolts, 78, and a seal therebetween effected by suitable gaskets, 8i and 82.

The walls, 84, of the piston, 16, and the piston skirt have a series of pressure equalization grooves, 86, formed therein to take the place of piston rings and by creating a turbulence between the piston skirt, 18, and the cylinder side Wall, 14, in the fluid leaking past the piston restricts the flow and reduces fluid leakage and also equalizes the pressure around the periphery of the piston.

The operation of the engine will now be described in view of the above description and the accompanying drawings. The working fluid is admitted to the receiving chamber, 58, through the piping, 70, and since the piston, 16, is biased in the direction of the receiving chamber by the spring, 34, the spring, 69, is positioned Within the recess, 38, but partially extends above the top surface of the piston. When the piston is near top dead center, the spring, 69, engages the bottom surface of the valve, 66, anl it is raised off its seat, 62, overcoming the biasing action of the spring, 64, on the stem, 66, and the pressure of the working fluid on the back surface of the admission valve, 60. Consequently the working fluid is allowed to pass through the valve seat, 62, and start the piston, 16, on its downward movement. As soon as the piston is removed from the contact with the valve, 68, the valve closes due to the action of the spring and cut-off of the admission fluid is accomplished. The fluid such as steam or any suitable thermodynamic fluid having similar properties expands in the cylinder doing work by forcing the piston downward against the action of the spring, 34, and the force of the connecting rod, 26. In the process of doing this work the pressure of this fluid decreases to such a point that the exhaust valves, 48, are able to overcome the decreased pressure on the upper surface by the action of their individual springs, 50, and the exhaust valves open. The fluid is therefore allowed to exhaust through the exhaust ports to the lower part of the cylinder and then to the manifold, 22, from there to atmosphere or to a condenser. After exhausting the fluid from the top of the piston the spring member, 34, and the action of the crank forces the piston to the top of the cylinder for a repeat of the cycle. During the return upward stroke, the exhaust valves, 44, remain open, thus retaining the pressure within the cylinder, 12, at exhaust pressure conditions, thus eliminating the usual back pressure on the piston during the compression stroke.

While there have been described herein what are at present considered to be preferred embodiments of the invention, it will be obvious to those skilled in the art that modifications and changes may be made without departing from the essence of the invention. It is therefore to be understood that the exemplary embodiments are illustrative and not restrictive of the invention, the scope of which is defined in the appended claims and that all modifications that come within the meaning and range of equivalency of the claims are intended to be included herein.

What is claimed is:

1. A reciprocating uniflow engine including a cylinder having an exhaust manifold at one end thereof, a piston moveable in said cylinder, normally spring biased away from said manifold, a fluid receiving chamber positioned at the other end of said cylinder, a valve seat concentrically formed in one wall of said receiving chamber providing an opening into said cylinder, a fluid admission valve normally spring biased into engagement with said seat, resilient means extending above said piston adapted for striking engagement with said admission valve, exhaust ports extending through said piston and exhaust valve means carried by said piston and moveable therewith, plungers mounted on said piston adapted to normally bias said exhaust valve means open, whereby at a position of the work stroke said plungers will overcome the fluid pressure on the exhaust valve means and lift the exhaust valve means permitting a free flow, said piston for striking engagement with said admission valve and plunger means carried by said piston normally spring biased into engagement with said exhaust valve means, said exhaust valve means responding to fluid pressure on the piston surface to maintain said valve in a closed position.

2. A reciprocating engine as set forth in claim 1 where said piston has a skirt on which are formed a plurality of longitudinally spaced pressure equalization prooves on the periphery thereof whereby leakage of fluid between the cylinder wall and piston is reduced to a minimum due to turbulence created by the grooves.

3. A reciprocating uniflow steam engine as set forth in claim 1 where said piston and cylinder are formed of a high density graphite whereby friction losses between cooperating surfaces are reduced to a minimum.

References Cited UNITED STATES PATENTS 1,045,956 12/1912 Demmler 91-268 2,120,992 6/1938 Soiden 91-224 2,419,859 4/1941 Tarr et a1. 9l--229 2,649,078 8/1953 Kelly 91-229 2,752,890 7/1956 Rogneby 91-401 3,173,341 3/1965 Carpenter 91-401 FOREIGN PATENTS 889,677 10/ 1943 France.

EDGAR W. GEOGHEGAN, Pl imary Examiner.

PAUL E. MASLOUSKY, Examiner. 

